Vane pump with annular elastomeric vane-projecting springs



Oct.

C. W. LITTLE, JR

VANE PUMP WITH ANNULAR ELASTOMERIC VANE-PROJECTING SPRINGS Filed NOV. 9,1967 INV EN Tc z knee/vrs wb2-22g; Jg

BY AM, MLLIMQMMPMMAI ATTQRNEYS United States Patent O 3,473,478 VANEPUMP WITH ANNULAR ELASTOMERIC JANE-PROJECTING SPRINGS Clarence W.Little, Sir., Brookfield, Wis., assignor, by

mesne assignments, to Waukesha Foundry Company,

Inc., a corporation of Wisconsin Filed Nov. 9, 1967, Ser. No. 681,859Int. Cl. Fltc 1/00; F01c 1/00; F011 1/26 US. Cl. 103-136 3 ClaimsABSTRACT F THE DISCLOSURE A rotor has slots within which vanes areguided for radial movement. To make the vanes follow the innerperipheral surfaces of the chamber, particularly when sticky oroleaginous materials are being pumped, the vanes are subjected to aradial thrust of one or more centripetally deformable elastomeric annuliconfined at each end of the rotor to lie in planes to which the rotoraxis is normal, the resilient rings being deformed in the course of vanemovement.

BACKGROUND OF THE INVENTION Some vane pumps are operated at speeds whichare suicient so that centrifugal force 0n the vanes assures continuousContact of the outer margins of the vanes with the interior contour ofthe pump body, regardless of viscosity of the materials pumped. In otherpumps, leaf or coil springs and camming guides operate the vanes.

None of these expcdients as heretofore used has been found acceptablefor the instant pump, which is especially designed for handling foodproducts and hence must be easily cleaned. This requires facility indisassembling and reassembling the parts and it requires that thesprings used will function dependably even when exposed to materialswhich might clog coil or leaf springs or resist movement of the vanes.

In the particular embodiment hereinafter disclosed, the vanes are lightplastic vanes of low mass and they rotate at speeds of only 1800 rpm.Hence the use of radial loading is essential. However, the contour ofthe pump casing is not a simple circular contour. This makes impracticalthe use of circular tracks or cams. The small size of the pump and thesanitary requirements make it impractical to use coil, wave or leafsprings, all of which require relatively minute cavities for housingthem. Such cavities are not easily cleanable.

The use of the pump in locations remote from large industrial centersrequires that the parts be such as to be readily obtainable. This pumpuses parts which are available for other purposes and are not speciallydesigned for this one service.

SUMMARY OF THE INVENTION All of these requirements are met by theinstant invention in which the vanes are radially biased outwardly atboth ends of the driving rotor by O-rings such as are conventionallyused for packing but are here used as elastomeric springs. These O-ringsare deformed when the vanes move inwardly, thus developing radial thrustfor assisting the outward return of respective vanes. The O-rings may besolid or tubular in cross section. To preclude axial deformation, thesprings are preferably confined in cavities formed in the respectiveends of the rotor.

The cross section and diametrical sizes of the O-ring and the elasticcharacteristics of the material of the O- ring are selected to provideadequate radial thrust to hold the several vanes outwardly against theinner periphery of the pump casing and thereby to overcome thestickiness of butter fat and other materials without exerting so great"ice a force as to cause undue wear on the vanes or the pump body. Itwill be understood that plural rings may be used instead of single ringsat each end of the rotor, if desired.

The elastomeric material of the O-rings may be any natural or syntheticrubber 0r resin which will withstand deections of the magnitude hereinvolved without fatigue failure, the material also being impervious andwith a surface readiy cleaned to meet sanitary requirements.

The fact that the O-ring is conned in a cavity which requires itsvane-displaced portion to be deformed by local deflection rather than bychange of form of the entire ring, such as might occur in open space,provides additional vane-restoring stress.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view taken in section onthe line 1-1 of FIG. 2 showing a pump embodying my invention, the rotorand vanes being illustrated in end elevation and parts being brokenaway.

FIG. 2 is a view in axial section on the line 2-2 of FIG. 1.

FIG. 3 is a perspective view of the pump rotor with a vane and springshown separately.

DESCRIPTION OF THE PREFERRED EMBODIMENT The pump shaft 6 drives anextension 7 which has bearings in casing 8 and supports rotor 10 in apump chamber 12. The inner peripheral wall surface 14 is non-concentricwith shaft extension 7 and may be either circular or noncircular,according to pump requirements.

The rotor 10 has generally radial slots at 16 for the radiallyreciprocable vanes 18. In the course of rotation of rotor 10, theinter-vane spaces between the rotor and the pump chamber vary in volumein known manner to receive fluid from inlet port 20 and to discharge itfrom outlet port 22.

The material of which the vanes are made may be varied. In a particularpump exemplifying the invention, these vanes are made of light plasticmaterial such as synthetic resin; they have little mass and at nominaloperational speeds are on the order of 1800 r.p.m., they do not developa great deal of centrifugal force such as might be required to holdtheir outer margins 24 in continuous contact with the Wall 14 of thepump casing 8.

Therefore the action of centrifugal force on the vanes is desirablysupplemented by spring means. Because the pump here disclosed is asanitary pump, where all parts require frequent and thorough cleansing,the spring means acting radially on the vanes 18 comprises elastomericO- rings 30 which are set in undercut channels 32 at the respective endsof the rotor 10 and are peripherally engaged beneath the ends of therespective vanes. The slots 16 open into channels 32 and the vane endsextend across such channels substantially to end walls 34 and 36.

The peripheral confinement of the respective O-rings prevents them fromoverall deformation under the pressure of the vanes as the latter areforced into engagement by camming action of the casing. If overalldeformation were possible, the reaction force exerted by the O-ring uponthe vanes would be relatively slight. Since, however, the O-rings areconfined and cannot assume an elliptical form under centripetalpressure, the deflection is localized and the O-ring is deformed in theimmediate vicinity of each respective vane which is exerting pressure onthe O- ring. This is clearly shown in FIG. 1 where the vane at the leftof the view is causing maximum deection of O-ring portion 38 and the twovanes at top and bottom are deecting the 0-ring spring 30 to a moderateextent at 40 and 42, while the spring is deformed very little at 44where it engages the vane at the right.

The undercutting of channels 32 as best shown at 46 in FIG. 3 leavesflanges 48 which overhang the O-ring springs to hold them in the desiredplane and to prevent axial deformation.

While the instant invention is not directly concerned with pump casingdesign, it Will be noted that the casing 8 comprises a bearing section50 having projecting dowel pins 52 for positioning end wall section 34and body section 54. Screws 56 with manually operable wing heads 58 passsuccessively through end wall section 36, body section 54, and end wallsection 34 into ange portion 60 of bearing section 50. Removal of thesescrews permits complete separation and removal for cleaning of all partscontacted by the fluid pumped. All surfaces will be fully exposed whenthe sections are separated and the springs and vanes removed.

Use of the bypass fitting `62 with its spring-loaded valve 64 is,ofcourse, optional. As shown, a bypass port 66, controlled by valve 64,connects outlet extension 68 t0 inlet extension 70 to relieve excessivedischarge pressure.

I claim:

1. A pump comprising the combination of a rotor having generally radialslots opening to its periphery, vanes mounted for reciprocation in saidslots, a casing having a pump chamber with a wall portion which is notconcentric with regard to the rotor and which has inlet and outletports, the rotor having at its axial ends cavities encircled by undercutchannels with which the rotor is provided and which open inwardly intothe respective cavities, and an elastomeric O-ring confined in each ofthe cavities and engaging the inner-ends of said vanes, said vanesextending axially across portions of the cavities and having portionsexposed in said channels, the O-rings having portions engaged in thechannels between each successive pair of vanes and externally continedthereby between points of O-ring engagement with said vanes, the saidchannels holding the respective O-rings substantially in theirrespective planes during the reciprocation of said vanes.

2. A pump according to claim 1 in which the pump is a sanitary pump andthe pump casing comprises a body portion substantially coextensiveaxially with the rotor and end plates detachably engaging the endsurfaces of the body portion of the casing and conning the rotor and theO-rings, the rotor and vanes and O-rings being freely and completelyremovable and separable for cleaning when at least one of the end platesis removed from the casing.

3. A pump according to claim 1 in which said elastomeric O-rings aresubstantially corresponding in radius to said cavities except asdeformed by said vanes.

References Cited UNITED STATES PATENTS 2,359,558 10/1944 Holl. 2,565,0778/1951 Holl. 3,191,503 6/1965 Fuehrer 9ll40 3,387,565 6/1968 Mezzetta2.30-153 X DONLEY J. STOCKING, Primary Examiner W. I. KRAUSS, AssistantExaminer U.S. Cl. X.R.

